Bone screws have been used in spinal instrumentation since at least as early as the 1960s. A bone screw is a screw that is usually made of titanium and perhaps finished with inert titanium nitride (gold colored finish). If a bone screw is used in a pedicle of the spine, then it is called a pedicle screw. Pedicle screws are most often used as part of a system of screws, plates and rods that immobilize part of the spine. During anterior fixation or plating of cervical vertebral bodies, the spine is approached from an anterior or anterlo-lateral direction and bone screws are typically used to solidly mount a spinal plate to the affected vertebrae. This helps spinal fusion wherein two or more vertebrae are encouraged to grow together after damage to the intervening disks or spinal fracture makes the original structure unstable.
Current pedicle screws require multiple steps in order to implant the screw in the pedicle. Typically, these steps include creating a starting hole with a very small drill bit, pedicle or bone probe, or awl. Once the starter hole is created, a bigger drill bit or pedicle probe may be used to create a pilot hole. After the pilot hole has been created, the pilot hole may then be tapped in a size compatible with the threads of the pedicle screw using a tap. Some pedicle screws are self-tapping thereby eliminating the step of tapping the pilot hole. Some bone screws, not pedicle screws, include a drill-bit feature associated with a thread and shaft. Each additional step required during a surgical procedure requiring the use of bone screws creates a greater potential for the patient to experience complications from the procedure as well as the chances for a physician to make a mistake due to fatigue during long constructs requiring numerous bone screws.
Thus, there remains a need for improved, inexpensive, and easy to use bone screws and methods for inserting bone screws in bone that minimize the need for preparatory steps prior to insertion of the bone screws into the bone.